The Color Of Your STOOL Says THIS About Your Health Check Your ! The Quantity of Blood Required to Produce a Tarry Stool. How much? Melena, characterized by black tarry stools, can occur with as little as 50 cc of blood in the stomach. How Stool Colors and What They Can Tell You Your stool color can carry important clues about digestion, diet, or even disease. Most shades are harmless, but some changes signal the need for What Does It Mean If My Poop Is Black? Melena Guide Decisions: A 20 year old male with dark stool Department of Emergency Medicine Saint John